U.S. patent application number 10/955242 was filed with the patent office on 2006-03-30 for active session mobility solution for radio link protocol.
Invention is credited to Sarit Mukherjee, Sureshbabu P. Nair, Priya Rajan, Ajay Rajkumar, Sampath Rangarajan, Das Suman, Michael D. Turner, Harish Viswanathan.
Application Number | 20060067273 10/955242 |
Document ID | / |
Family ID | 35519890 |
Filed Date | 2006-03-30 |
United States Patent
Application |
20060067273 |
Kind Code |
A1 |
Suman; Das ; et al. |
March 30, 2006 |
Active session mobility solution for radio link protocol
Abstract
An active session mobility solution for radio link protocol
(RLP) in accordance with the present invention defines two RLP
migrations states. A first state is defined as a forward-link RLP
state and depicts the communication of data from a home agent to an
access terminal in an IP network. A second state is defined as a
reverse-link RLP state and depicts the communication of data from
the access terminal to the home agent in the IP network. In one
embodiment of the seamless active session mobility solution for RLP
in accordance with the present invention, a two-stage RLP transfer
process for the migration of the two defined states from a source
to a target is implemented. In a first stage, the forward-link RLP
state is transferred from a source to a target. In a second stage,
frame selection and the reverse-link RLP are transferred from the
source to the target.
Inventors: |
Suman; Das; (Scotch Plains,
NJ) ; Mukherjee; Sarit; (Morganville, NJ) ;
Nair; Sureshbabu P.; (Whippany, NJ) ; Rajan;
Priya; (Somerset, NJ) ; Rajkumar; Ajay;
(Morristown, NJ) ; Rangarajan; Sampath;
(Bridgewater, NJ) ; Turner; Michael D.; (Madison,
NJ) ; Viswanathan; Harish; (Basking Ridge,
NJ) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP/;LUCENT TECHNOLOGIES, INC
595 SHREWSBURY AVENUE
SHREWSBURY
NJ
07702
US
|
Family ID: |
35519890 |
Appl. No.: |
10/955242 |
Filed: |
September 30, 2004 |
Current U.S.
Class: |
370/331 ;
370/338 |
Current CPC
Class: |
H04W 8/087 20130101;
H04W 80/00 20130101 |
Class at
Publication: |
370/331 ;
370/338 |
International
Class: |
H04Q 7/00 20060101
H04Q007/00 |
Claims
1. A method for seamless active session migration of a reliable
protocol from a source to a target in a wireless IP network,
comprising: decoupling said reliable protocol into at least a
forward-link state and a reverse-link state; and migrating at least
said forward-link state and said reverse-link state from said
source to said target.
2. The method of claim 1, wherein at least said forward-link state
is migrated from said source to said target in a first stage of
migration and at least said reverse-link state is migrated from
said source to said target in a second stage of migration.
3. The method of claim 2, wherein said first stage of migration
comprises: transmitting, to said source and to said target, a
signal indicating an imminent migration of said forward-link state
of said reliable protocol from said source to said target;
tunneling, upon receipt of said signal by said source, forward-link
data segmented by said source and state information of said
forward-link data segmented by said source to said target;
transmitting from said target to said source an acknowledgment
indicating the readiness of said target to receive the migration of
said forward-link state of said reliable protocol from said source;
and tunneling, upon receipt of said acknowledgment by said source,
pre-segmented forward-link data from said source to said
target.
4. The method of claim 3, wherein said state information of said
forward-link data segmented by said source is tunneled to said
target in parallel with said forward-link data segmented by said
source so as to prevent stalling of information flow to said access
terminal.
5. The method of claim 3, wherein said pre segmented forward-link
data tunneled by said source to said target is segmented by said
target and communicated by said target to an access terminal.
6. The method of claim 3, wherein said pre-segmented forward-link
data tunneled by said source to said target is tunneled by said
target to a second target.
7. The method of claim 6, wherein said second target is a target
from which an access terminal is receiving a stronger pilot
signal.
8. The method of claim 6, wherein said pre-segmented forward-link
data tunneled by said target to said second target is segmented by
said second target and communicated by said second target to an
access terminal.
9. The method of claim 3, wherein said source further communicates
a sequence number to said target, said sequence number defining an
octet in a sequence of octets of said forward-link data with which
segmenting of forward-link data will commence at said target if
said source receives said acknowledgment from said target before
the arrival of said octet at said source.
10. The method of claim 2, wherein said first stage of migration
comprises: transmitting, to said source and to said target, an
early indication signal indicating a possible migration of said
forward-link state of said reliable protocol from said source to
said target; tunneling, upon receipt of said early indication
signal, a copy of data received by said source to said target;
transmitting, to said source and to said target, a migration signal
indicating an imminent migration of said forward-link state of said
reliable protocol from said source to said target; tunneling, upon
receipt of said migration signal, pre-segmented forward-link data
from said source to said target.
11. The method of claim 10, wherein because said target receives a
copy of the data received by said source, segmenting of said
forward-link data may commence in said target with the receipt of
said migration signal.
12. The method of claim 10, wherein said source, upon receipt of
said migration signal, communicates a sequence number to said
target, said sequence number defining an octet in a sequence of
octets of said forward-link data with which segmenting of
forward-link data will commence at said target.
13. The method of claim 2, wherein said second stage of migration
comprises: communicating, from said source to at least said target,
a signal indicating that frame selection will be performed at said
target beginning with a next expected reverse-link octet of
reverse-link data; communicating, from said source to said target,
a sequence number of said next expected reverse-link octet of
reverse-link data; forwarding reverse-link octets of said
reverse-link data having sequence numbers less than the sequence
number of said next expected reverse-link octet to said source to
be segmented by said source and communicated toward a home agent;
and forwarding reverse-link octets having sequence numbers greater
than or equal to the sequence number of said next expected
reverse-link octet to said target to be buffered by said
target.
14. The method of claim 13, wherein said source informs said target
when a reverse-link octet having a sequence number one before the
sequence number of said next expected reverse-link octet has been
processed by said source and communicated by said source toward
said home agent, such that said target may begin processing
buffered and newly received octets and communicating said buffered
and newly received octets toward said home agent.
15. The method of claim 1, further comprising: performing
MAC/scheduling functions in said target upon the migration of said
forward-link state to said target.
16. The method of claim 1, further comprising: performing frame
selection in said target upon the migration of said reverse-link
state to said target.
17. The method of claim 1, wherein said reliable protocol comprises
a radio link protocol.
18. The method of claim 1, wherein said source and said target
comprise base station routers.
19. The method of claim 1, wherein said source and said target
comprise radio network controllers (RNCs).
20. A method for seamless active session migration of a reliable
protocol session from a source to a target, comprising: decoupling
said reliable protocol session into at least a first state and a
second state; communicating, to said source and to said target, a
signal indicating an imminent migration of at least said first
state of said reliable protocol session from said source to said
target; forwarding, upon receipt of said signal by said source, IP
data segmented by said source to said target; communicating from
said target to said source a signal indicating the readiness of
said target to receive the migration of said first state of said
reliable protocol session from said source; and forwarding, upon
receipt of said signal from said target by said source,
pre-segmented IP data from said source to said target.
21. The method of claim 20, further comprising: communicating, from
said source to at least said target, a signal indicating that frame
selection will be performed at said target beginning with a next
expected octet of IP data, triggering the migration of said second
state to said target; communicating, from said source to said
target, a sequence number of said next expected octet of IP data;
forwarding octets of said IP data having sequence numbers less than
the sequence number of said next expected reverse-link octet to
said source; and forwarding octets having sequence numbers greater
than or equal to the sequence number of said next expected octet to
said target to be buffered by said target.
22. The method of claim 20, wherein at least said first state is
migrated from said source to said target in a first stage of
migration and at least said second state is migrated from said
source to said target in a second stage of migration.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to mobile communications
systems and, more specifically, to mobility management techniques
in such systems that support multimedia applications in a highly
dynamic Internet Protocol-based networking environment.
BACKGROUND OF THE INVENTION
[0002] Considerable attention has been directed toward the
implementation of mobile telecommunication service in computer data
networks, and particularly the ability to route communication
content to mobile wireless nodes that routinely connect to the data
network at different points of attachment, via air interfaces.
These include cellular telephones, Personal Digital Assistants
(PDAs), laptop computers, and other mobile wireless communication
equipment.
[0003] To facilitate mobile wireless telecommunication service in a
data network, it is desirable (although not always possible) to
allow mobile wireless nodes to change their link-layer point of
network attachment without reassigning a new network address.
According to current data network telecommunication standards for
mobile equipment in general (e.g., the "Mobile IP" standards
promulgated by the Internet Engineering Task Force (IETF) or the
General Packet Radio Service (GPRS) standards proposed by the
European Telecommunication Standards Institute (ETSI)), one way to
provide the desired network address transparency is to employ
"mobility agents." These are network routing nodes that route
communication content on behalf of mobile nodes as they move around
the network. For example, according to the IETF Mobile IP
standards, a mobile node's mobility agents may consist of a "home
agent" routing node and may also include a "foreign agent" routing
node. The home agent is a routing node in the mobile node's
subnetwork that maintains a network interface on the link indicated
by the mobile node's "home address," which is a network address
intended to remain assigned to the mobile node for an extended time
period. When the mobile node is away from its home subnetwork, the
home agent intercepts communication content bound for the mobile
node's home address and tunnels it for delivery to a "care-of"
address assigned to the mobile node when the mobile node registers
on a foreign subnetwork. The care-of address may be the address of
a foreign agent routing node in the foreign subnetwork.
[0004] Correspondent nodes wishing to communicate with a
foreign-registered mobile node are able to address their
communication content to the mobile node's home address.
Transparently, the communication content is tunneled to the mobile
node's care-of address and delivered to the mobile node on the
foreign subnetwork. Normal routing may be used for sending return
communication content from the mobile node to the correspondent
node.
[0005] Some link-level protocols used to support mobile node
communications include a Point-to-Point Protocol and a Radio Link
Protocol. Protocols typically utilized in non-mobile applications,
such as the Internet Protocol (IP) and the Point-to-Point protocol
(PPP), are layered on top of a lower level mobile protocol, such as
the Radio Link Protocol (RLP) defined by the Third Generation
Partnership Project 2 (3GPP2). More specifically, when a mobile
node connects to a gateway on the Internet, a Point-to-Point
Protocol (PPP) session is typically established between the mobile
node and the gateway device. As is known in the art, PPP is used to
encapsulate network layer datagrams over a serial communications
link. For more information on PPP see Internet Engineering Task
Force ("IETF") Request for Comments ("RFC"), RFC-1661, RFC-1662 and
RFC-1663 incorporated herein by reference in its entirety. The
gateway, or tunnel initiator, typically initiates establishment of
a tunnel connection to a tunnel endpoint server. For example, when
a mobile node is connected to a foreign agent, a connection
oriented point-to-point communication link, such as a Layer 2
Tunneling Protocol (L2TP) tunnel, is typically established between
the foreign agent and the home agent to permit the transfer of data
to and from the mobile node. See Layer Two Tunnelling Protocol
(L2TP), Request for Comment (RFC) 2661, A. Valencia, et al., June
1999, herein incorporated by reference in its entirety.
[0006] In a wireless environment, reliable end to end transmission
is commonly provided by a Radio Link Protocol (RLP) that is highly
optimized for the particular wireless transmission media that are
in use. Examples of RLP protocols can be found in TIA/EIA IS-707
(for CDMA) and IS-135 (for TDMA). RLP is a reliable link protocol
that allows retransmission from a source to a destination of the
link of lost control packets or lost new and retransmitted data
packets. The scheme allows the sender to retransmit the
unacknowledged or negatively acknowledged packets preemptively at
the link layer rather than rely on end-to-end retransmissions by
higher layer protocols. This scheme can efficiently improve
performance since it prevents end-to-end retransmissions and
transport layer time-outs. The foregoing routing mechanisms may
also be used for mobile wireless nodes connected to a foreign
subnetwork via an air interface. However, a problem may arise if
the mobile wireless node is being actively transported while
communicating over the data network and a call handoff is required
from one radio base station to another. In that case, the old base
station may be linked to one foreign agent, while the new base
station is linked to another foreign agent. Call handoff then
requires that the communication tunneling endpoint be transferred
from the old care-of address to the new care-of address.
[0007] This may create gaps that interrupt the timely delivery of
call content, which can degrade communication quality, particularly
for voice telephony. Such gaps arise from the inability of the data
network to coordinate well with the air interface so as to
determine the exact time of handoff. Delay can occur between the
point of handoff and the point at which the home agent begins
routing communication content to the new care-of address.
[0008] Accordingly, there is a need in a data network
telecommunication system serving mobile wireless nodes for improved
call handoff without loss of communication content. What is
required is a system and method that seamlessly routes
communication content during handoff so that the mobile wireless
node does not experience noticeable communication content loss or
delay other than that caused by the air interface, if any.
SUMMARY OF THE INVENTION
[0009] The present invention addresses various deficiencies of the
prior art by providing a seamless active session migration solution
for a reliable protocol such as radio link protocol.
[0010] In one embodiment of the present invention, a method for
seamless active session migration of a radio link protocol from a
source to a target in a wireless IP network includes decoupling the
radio link protocol into at least a forward-link state and a
reverse-link state and migrating at least the forward-link state
from the source to the target in a first stage of migration and
migrating at least the reverse-link state from the source to the
target in a second stage of migration.
[0011] In an alternate embodiment of the present invention, a first
stage of migration of the decoupled radio link protocol includes
transmitting, to the source and to the target, a signal indicating
an imminent migration of the forward-link state of the radio link
protocol from the source to the target, tunneling, upon receipt of
the signal by the source, forward-link data segmented by the source
to the target, the segmented data to be communicated by the target
to an access terminal, transmitting from the target to the source
an acknowledgment indicating the readiness of the target to receive
the migration of the forward-link state of the radio link protocol
from the source and tunneling, upon receipt of the acknowledgment
by the source, pre-segmented forward-link data from the source to
the target to be segmented by the target and communicated by the
target to an access terminal.
[0012] In an alternate embodiment of the present invention, a
second stage of migration of a decoupled radio link protocol
includes transmitting, from the source to at least the target, a
signal indicating that frame selection is to be performed by the
target, transmitting, from the source to the target, a sequence
number of a next expected reverse-link octet, forwarding
reverse-link octets having sequence numbers less than the sequence
number of the next expected reverse-link octet to the source to be
segmented by the source and communicated toward a home agent, and
forwarding reverse-link octets having sequence numbers greater than
or equal to the sequence number of the next expected reverse-link
octet to the target to be segmented by the target and communicated
toward the home agent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The teachings of the present invention can be readily
understood by considering the following detailed description in
conjunction with the accompanying drawings, in which:
[0014] FIG. 1 depicts a high level block diagram of a conventional
CDMA hierarchical wireless IP network;
[0015] FIG. 2 depicts a high level block diagram of a
Base-Station-Router (BSR) type network architecture where an
embodiment of the present invention may be applied;
[0016] FIG. 3 depicts a high level functional diagram of the BSR
network of FIG. 1 during an initial state in which a first BSR is
functioning as a Source BSR for a mobile;
[0017] FIG. 4 depicts a high level functional diagram of the BSR
network of FIG. 1 during a state when the mobile begins to receive
a stronger signal from a second BSR (Target BSR) and chooses to
receive its data from the Target BSR;
[0018] FIG. 5 depicts a high level block diagram of a method for
active session mobility for forward-link radio link protocol
(F-RLP) in accordance with an embodiment of the present
invention;
[0019] FIG. 6 depicts a high level functional diagram of the BSR
network of FIG. 1 after transfer of the F-RLP from the Source BSR
to the Target BSR;
[0020] FIG. 7 depicts a high level block diagram of a method for
active session mobility for R-RLP in accordance with an embodiment
of the present invention; and
[0021] FIG. 8 depicts a high level functional diagram of the BSR
network of FIG. 1 after the transfer of the F-RLP and R-RLP from
the Source BSR to the Target BSR.
[0022] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The present invention advantageously provides a seamless
active session mobility solution for reliable protocols such as a
Radio Link Protocol (RLP). Although various embodiments of the
present invention are described herein with respect to an RLP
protocol being used in a flat network architecture based on base
station routers (BSRs) described in a commonly assigned patent
application entitled "A wireless communications system employing a
network active set formed from base stations operable as primary
and secondary agents", the specific embodiments of the present
invention should not be treated as limiting the scope of the
invention. It will be appreciated by those skilled in the art and
informed by the teachings of the present invention that the active
session mobility solution of the present invention may be
advantageously implemented in substantially any network
implementing a reliable protocol, such as a conventional CDMA
hierarchical network implementing RLP or a UMTS network based on
the General Packet Radio Service (GPRS) model implementing a radio
link control (RLC) protocol.
[0024] To assist in the description of various mobile IP protocols
associated with the implementation of various embodiments of the
present invention, the inventors herein depict a conventional
hierarchical CDMA wireless IP network. FIG. 1 depicts a high level
block diagram of a conventional CDMA hierarchical wireless IP
network. The hierarchical CDMA network 100 of FIG. 1 comprises an
access terminal (AT) 110, a Base Transceiver Station (BTS) 115, a
RAN router 120, a radio network controller (RNC) 125, a PDSN 130,
an IP network 140 and an Internet service provider (ISP) 145.
Although the CDMA network 100 of FIG. 1 further depicts a RADIUS
Authentication, Authorization, and Accounting (AAA) server 135, the
AAA server 135 is merely depicted for providing a complete
depiction of the CDMA network 100. As the function of the AAA
server 135 is ancillary to the concepts of the present invention,
the AAA server 135 will not be described herein.
[0025] In the hierarchical CDMA network 100 of FIG. 1, the BTS 115
performs the function of interfacing to the AT 110 over the air
interface. It contains the hardware and software to perform the
digital signal processing required to implement the air interface,
and to communicate with back-end servers and routers. The HCS 115
also contains the RF components required to transmit the signals
over the air, and to receive the RF signals from the AT 110.
[0026] The RAN Router 120 provides a common point in the CDMA
network 100 where the back haul interfaces from several BTSs may
terminate. This function is required to allow routing of
information received from the air interface to a control point for
a session, where frame selection can be performed. The RAN router
120 also allows routing of data between the BTSs and the ISP 145 in
a global internet.
[0027] The RNC 125 provides signaling and traffic processing
control for each session. These functions include session
establishment and release, frame selection and Radio Link Protocol
(RLP) processing. As previously mentioned, RLP is a reliable link
protocol between, for example the AT 110 and the RNC 125, that
allows retransmission from a source to a destination of the link of
lost control packets or lost new and retransmitted data packets.
The scheme allows the sender to retransmit the unacknowledged or
negatively acknowledged packets preemptively at the link layer
rather than rely on end-to-end retransmissions by higher layer
protocols. This scheme can efficiently improve performance since it
prevents end-to-end retransmissions and transport layer time-outs.
The RNC 125 provides the processing for the standard interface to
the PDSN 130 and allows the RNC functions to interface to the PDSN
130. The RNC 125 terminates all mobility management functions of
the radio network, and is the demarcation point between the Radio
Network and the IP Network 140 which ultimately communicates with
the ISP 145.
[0028] The PDSN 130 terminates the point-to-point protocols (PPP),
and/or generates a tunnel to a Layer 2 Tunnel Protocol Network
Server (LNS) if L2TP Internet access is being used. The PDSN 130
resides in the serving network, and is allocated by the serving
network where the AT 110 initiates a service session. The PDSN 130
terminates a residing PPP link protocol with the AT 110. The PDSN
130 serves as a Foreign Agent (FA) in the network 100. The PDSN 130
maintains link layer information and routes packets to external
packet data networks or to a Home Agent (HA) in the case of
tunneling to the HA. The PDSN 130 also maintains an interface to
the backbone IP network 140.
[0029] The PDSN 130 maintains a serving list and unique link layer
identifier for all the ATs that have an active session with the
PDSN 130. The PDSN 130 uses this unique link layer identifier to
reference each AT connected to the PDSN 130, and maintains an
association between the IP address of the AT and the HA address and
the link identifier. The link layer association is maintained at
the PDSN 130 even when the AT 110 is dormant. When the AT 110 moves
to a location served by a different RNC 125, the PDSN 130 interacts
with a new serving RNC to facilitate a handoff from the RNC with
which the AT 110 had an active session.
[0030] In contrast to the above hierarchical architecture of the
CDMA network 100 of FIG. 1, a flat network architecture is proposed
in a commonly assigned patent application entitled "A wireless
communications system employing a network active set formed from
base stations operable as primary and secondary agents", which
incorporates the RNC and PDSN functions together with the Cell Site
equipment into one network element that connects directly to the
Internet. This concept therefore has the potential to reduce the
cost and complexity of deploying a conventional hierarchical
network, and of adding new wireless access points (cell sites) to
an already deployed network. In such a flat network, deployment
cost is reduced compared with the traditional network architecture
because the centralized RNC functions and the centralized PDSN
functions are incorporated into the cell site equipment. Also,
there is a potential to reduce the delay experienced by a wireless
user, because the packet queuing delays at the PDSN and at the RNC
are removed. Such a flat architecture is referred to as a
Base-Station-Router (BSR) type network architecture.
[0031] For example, FIG. 2 depicts a high level block diagram of a
novel Base-Station-Router (BSR) type network architecture where an
embodiment of the present invention may be applied. Such a
Base-Station-Router type network architecture is described in
commonly assigned U.S. patent application entitled "A wireless
communications system employing a network active set formed from
base stations operable as primary and secondary agents", which is
herein incorporated by reference in its entirety. The BSR network
200 of FIG. 2 illustratively comprises an access terminal (AT) 210
(also referred to as a mobile herein), a plurality of base station
routers (BSRs) (illustratively 3 BSRs) 220.sub.1-220.sub.3, a core
network 230, a home agent (HA) 240 and an IP Internet 250. In the
BSR network 200 of FIG. 2, unlike in conventional IP networks,
radio network control functions such as call admission control,
CDMA code tree management, and paging control are contained within
each of the base station routers 220.sub.1-220.sub.3. More
specifically, different ones of the base station routers
220.sub.1-220.sub.3 are able to serve as the primary agent (PA) for
different mobiles, unlike in conventional IP network architectures
where a single radio network controller (RNC) performs the resource
management for all of the mobiles of the set of base stations it
controls. In the BSR network 200 of FIG. 2, the core network 230
functions to ensure the efficient and timely delivery of data
packets between the BSRs 220.sub.1-220.sub.3. The core network 230
also operates to communicate the reverse link data from the BSRs
220.sub.1-220.sub.3 intended for the HA 240 to the IP Internet 250,
which forwards the data to the HA 240. In the forward link
direction, the core network 230 functions to communicate data
received from the HA 240 through the IP Internet 250 intended for
the mobile 210 to the BSRs 220.sub.1-220.sub.3.
[0032] In the BSR network 200 of FIG. 2, mobile 210 is in
communication with the three BSRs 220.sub.1-220.sub.3 which
comprise a network active set (NAS) of the mobile 210. Based on
changing radio conditions, mobile 210 may choose to receive data
from any of the BSRs within its NAS. Switching may occur on a fast
time scale. Within the NAS, one of the BSRs 220.sub.1-220.sub.3
functions as a primary agent (PA) while the other BSRs may function
as secondary agents (SA). The PA serves as the anchor for mobility
and radio resource management and performs function similar to the
RNC in traditional hierarchical network architectures. Although the
novel BSR network architecture described above greatly reduces the
number of components required in an IP network and thus greatly
reduces the costs associated with an IP network, in such BSR
network architectures there exist more handoffs between base
station routers due to the movement of an access terminal through
the network and, as such, a need exists for an efficient, active
session mobility solution for RLP. That is, in a BSR architecture,
each BSR serves as a base station, RNC, and PDSN. When an AT moves
across BSR nodes, it effectively moves across RNCs. Thus AT call
states are able to be moved in an active state. A staged state
movement approach may be chosen to enable a seamless handoff to the
new BSR and an inter-BSR interface will be used to tunnel, control
and traffic information between BSRs during mobility.
[0033] As in conventional CDMA systems, in the BSR network 200 of
FIG. 2, a mobile that powers up in the vicinity of the active set
of BSRs 220.sub.1-220.sub.3 acquires a pilot signal from each of
the BSRs 220.sub.1-220.sub.3 and uses the access channel to
communicate with the base station from which it received the
strongest signal to initiate a session. As previously mentioned,
the selected BSR having the strongest signal (initially and
illustratively BSR 220.sub.1) serves as a primary agent (PA) and,
as such, an access point for the mobile 210. In the BSR network 200
of FIG. 2, the BSR 220.sub.1 is considered the source BSR and
initially terminates the wireless base-station MAC protocol
normally maintained in a base station of a traditional hierarchical
network architecture, the RLP protocol normally maintained in a RNC
of a traditional hierarchical network architecture, as well as the
(point-to-point) PPP protocol normally maintained in a packet
serving data node (PDSN) of a traditional hierarchical network
architecture.
[0034] FIG. 3 depicts a high level functional diagram of the BSR
network 200 of FIG. 2 during an initial state in which the BSR
220.sub.1 is functioning as the PA (Source BSR) for the mobile 210.
BSR 220.sub.1 of FIG. 3 illustratively comprises a MAC/Scheduler
functional block (MAC/SCH.sub.1), an RLP functional block
(RLP.sub.1), a PPP functional block (PPP.sub.1), and an FA
functional block (FA.sub.1). Similarly, the BSR 220.sub.2 of FIG. 3
illustratively comprises a MAC/Scheduler functional block
(MAC/SCH.sub.2), an RLP functional block (RLP.sub.2), a PPP
functional block (PPP.sub.2), and an FA functional block
(FA.sub.2).
[0035] In accordance with various embodiments of the present
invention, a reliable protocol, such as RLP, is decoupled into a
forward-link RLP (F-RLP) component and a reverse-link RLP (R-RLP)
component. In the embodiments of the present invention described
herein, F-RLP is considered the direction of data flow from the HA
240 to the mobile 210 and R-RLP is considered the direction of data
flow from the mobile 210 to the HA 240. In at least the embodiment
of the seamless active session mobility solution for RLP of FIG. 3,
a component of the BSR migration strategy is to keep F-RLP and the
MAC/Scheduler co-located in a serving BSR (initially Source BSR
220.sub.1) to take advantage of scheduling efficiencies, avoid
time-consuming Mobile IP registrations with excessive movement of
the FA and as such the PPP endpoint, and keep interruption of
dataflow to a minimum, all while keeping usage of the backhaul
through tunnelling at a low level.
[0036] That is, initially, all processing of forward and
reverse-link data is co-located on the BSR 220.sub.1. To avoid
time-consuming Mobile IP registrations with the Home Agent, BSR
movement is realized by moving individual BSR components of the RLP
(e.g., the F-RLP and the R-RLP) in different stages. As a component
of the RLP is migrated to a target BSR, processing splits between
multiple BSRs, and tunnelling of data must be performed. Since
mobility is an expected condition, tunnelling has to be done as
components migrate to the new BSR. To minimize excessive backhaul
usage, tunnelling must be kept to a minimum.
[0037] With respect to the R-RLP, the location of the Frame
Selector does not affect the backhaul usage. No matter on which BSR
it resides, all of the other BSRs within the active set must tunnel
their reverse-link frames to the BSR with the Frame Selector
(initially Source BSR 220.sub.1). To maintain scheduling
efficiencies in the F-RLP direction, keeping the RLP co-located
with the MAC/Scheduler will yield the most benefits. When the
mobile 210 selects a new serving BSR (i.e., BSR 220.sub.2), the
mobile 210 will be served data through the new BSR's MAC/Scheduler
(i.e., MAC/SCH.sub.2). If the Frame Selector and the F-RLP move
together to the BSR 220.sub.2, there will be a tunnel required to
send R-RLP data back to the BSR's 220.sub.1 PPP and FA. This
data-flow is in addition to the F-RLP data-flow (tunnelled from PPP
to RLP) and the R-RLP data-flow (tunnelled from the MAC to the
Frame Selector). As such, this is not the preferred method. With
the forward link and reverse-link RLP components moving separately,
movement of the F-RLP, expected to happen often, follows the mobile
210 to the new BSR along with the serving MAC/Scheduler. This
allows for scheduling efficiencies to be achieved by co-locating
the F-RLP and the MAC/Scheduler. The R-RLP moves less often along
with PPP and FA, therefore, reducing costly Mobile-IP registrations
and PPP renegotiations.
[0038] For example, FIG. 4 depicts a high level functional diagram
of the BSR network 200 of FIG. 2 during a state when the mobile 210
begins to receive a stronger signal from the BSR 220.sub.2 than
from the BSR 220.sub.1 (Source BSR) and chooses to receive its data
from the BSR 220.sub.2 (Target BSR). That is, FIG. 4 depicts the
BSRs 220.sub.1-220.sub.2 during a handoff from the BSR 220.sub.1 to
the BSR 220.sub.2. In the embodiment of the present invention of
FIG. 4, the F-RLP is moved to the new serving BSR 220.sub.2 as soon
as the new BSR 220.sub.2 becomes the serving BSR (i.e. a handoff
notification such as the data rate control channel (DRC) points to
it). This is in keeping with the goal of not denying the MAC layer
data upon request from the mobile 210.
[0039] The RLP migration in accordance with an embodiment of the
present invention begins with migrating the F-RLP. Initially the
F-RLP exists on the Source BSR 220.sub.1 prior to migration. The
Source BSR 220.sub.1 is handling all forward-link traffic tasks
such as new data octets arriving from the PPP (PPP.sub.1), negative
acknowledgment messages (NAKs) processed for missing octets in the
data, and RLP frames being sent to the MAC/Scheduler
(MAC/SCH.sub.1) for transmission over-the-air to the mobile 210.
The first indication that a handoff will occur between the source
BSR 220.sub.1 and the target BSR 220.sub.2 is the receipt of a
notification from the mobile indicating a handoff request through
signals such as the data source control channel (DSC) or DRC. Upon
receipt of the DSC, the source BSR 220.sub.1 and the Target BSR
220.sub.2 become aware of the mobile's 210 desire to be served by
the Target BSR 220.sub.2.
[0040] In one embodiment of the present invention taking advantage
of early handoff notification (i.e., which may be in the form of a
DSC indicator), the source BSR 220.sub.1 and the Target BSR
220.sub.2 prepare for movement of the F-RLP by duplicating any
incoming octets to the Source F-RLP (RLP.sub.1) and tunnelling the
duplicated octets to the Target RLP (RLP.sub.2) along with the
starting sequence number of the first packet in the tunnel to be
stored in a buffer of the Target BSR 220.sub.2. The Source F-RLP
(RLP.sub.1) also transmits a copy of its buffered octets to the
Target RLP (RLP.sub.2) such that when the F-RLP is transferred to
the Target RLP (RLP.sub.2), the Target RLP (RLP.sub.2) is able to
transmit the data to the mobile 210 without losing any octets and
without transmitting the octets out of sequence. The Target RLP
(RLP.sub.2) is considered to be in the Pre-Serving stage of
migration. Furthermore, in various embodiments of the present
invention, along with the tunnelling of a copy of the duplicated
octets, a starting sequence number, and a copy of the buffered
octets to the Target RLP (RLP.sub.2), the Source F-RLP (RLP.sub.1)
also informs the Target RLP (RLP.sub.2) in parallel of the RLP
state transfer so as to prevent stalling of information flow to the
mobile 210.
[0041] The terms "data sequence number" and "sequence number" as
used throughout this disclosure will now be defined by the
inventors before continuing with the description of the various
embodiments of the invention. More specifically, when data is
tunneled between a source and a target, the data may be tunneled
over either a proprietary tunnel or a standard tunneling mechanism.
The tunneling mechanism that is used provides the sequencing by
providing for a sequence number in the encapsulating header.
Because various embodiments of the present invention described
herein implement a tunneling mechanism to forward data from a
source to a target and from a target to a source, is should herein
be assumed that the tunneling mechanism provides sequencing numbers
for the transferred data. As such, it should be noted that
throughout the description of the invention when the inventors
refer to a data sequence number or just a sequence number, the
inventors are referring to the sequence numbers given to data by
the tunneling mechanisms implemented by the various embodiments of
the present invention.
[0042] Subsequent to the transmission of the early handoff
notification (e.g., DSC), a handoff notification (i.e., such as a
data rate control channel (DRC)) is communicated to all of the
BSR's within an active set. The DRC indicates that the new serving
BSR is the Target BSR 220.sub.2. Alternatively, instead of a DRC
indication being communicated to all of the BSRs, the indication
that the new serving BSR is the Target BSR 220.sub.2 may be
affected by the termination of the early handoff notification
(e.g., the DSC). As such, the DRC or alternatively the termination
of the early notification (e.g., the DSC) indicates that the new
serving BSR is the Target BSR 220.sub.2. Upon the Target BSR
220.sub.2 becoming the serving BSR, the Source BSR 220.sub.1
transmits a last byte sequence number, V(S.sub.L), to the Target
BSR 220.sub.2. The last byte sequence number, V(S.sub.L), indicates
the last octet segmented by the Source BSR 220.sub.1. The F-RLP
processing (segmenting of data) begins at the Target BSR 220.sub.2
with the occurrence of the octet after the octet having the last
byte sequence number, V(S.sub.L). Alternatively and because the
Target BSR 220.sub.2 receives a copy and is informed of the status
of all of the octets received by and maintained in a buffer of the
Source BSR 220.sub.1, F-RLP processing may begin in the Target BSR
220.sub.2 immediately upon receipt of the handoff notification or
the expiration of the early handoff notification.
[0043] In addition to the forwarding of the copy of the octets, the
RLP (RLP.sub.1) of the Source BSR forwards any buffered NAKs to the
RLP (RLP.sub.2) of the Target BSR 220.sub.2. As such, any NAKs
generated for the retransmission of a lost octet may be serviced by
the Target BSR 220.sub.2. Therefore, the Source RLP (RLP.sub.1)
becomes non-serving and the mobile 210 is served forward-link data
from the Target RLP (RLP.sub.2). As such, now in the forward-link
direction, the HA 240 sends forward-link data to the FA (FA.sub.1)
of the Source BSR 220.sub.1. The Source FA (FA.sub.1) then sends
the forward-link data to the PPP (PPP.sub.1) of the Source BSR
220.sub.1 which tunnels the forward-link data to the PPP
(PPP.sub.2) of the Target BSR 220.sub.2. The Target PPP (PPP.sub.2)
then communicates the forward-link data to the RLP (F-RLP) of the
Target BSR 220.sub.2 which sends the forward-link data to the MAC
Scheduler (MAC/SCH.sub.2) of the Target BSR 220.sub.2 which
ultimately communicates the forward-link data to the mobile 210
over the air.
[0044] In an embodiment of the present invention having no early
notification, the RLP (RLP.sub.1) of the Source BSR 220.sub.1
begins tunnelling segmented data to the RLP (RLP.sub.2) of the
Target BSR 220.sub.2 with the receipt of the DRC indicating a
handover to the target. In addition, the Source BSR 220.sub.1
records a sequence number, V(S), of an octet being segmented when
the DRC was received. The Source BSR 220.sub.1 determines a future
sequence number, V(S+x), and transmits both sequence numbers to the
Target BSR 220.sub.2 indicating the intention to complete the
migration of the F-RLP before the receipt of an octet having the
future sequence number, V(S+x). The Target BSR 220.sub.2 receives
both sequence numbers and updates the sequence number as data
arrives. If an acknowledgement is not received from the Target BSR
220.sub.2 accepting the assignment before the occurrence of the
future sequence number V(S+x), segmenting of the data continues in
the RLP (RLP.sub.1) of the Source BSR and the segmented octets are
forwarded from the RLP (RLP,) of the Source BSR 220.sub.1 to the
RLP (RLP.sub.2) of the Target BSR 220.sub.2. The Source BSR
220.sub.1 then selects a second future sequence number, V(S+nx),
and forwards the second future sequence number V(S+nx) to the
Target BSR 220.sub.2. This process continues until the Target BSR
220.sub.2 transmits an acknowledgment to the Source BSR 220.sub.1
accepting the assignment before a sequence number determined by the
Source BSR 220.sub.1. That is, upon acknowledgment by the Target
BSR 220.sub.2, octets having a sequence number less than or equal
to, for example in a first iteration, V(S+x) are continued to be
segmented in the Source BSR 220.sub.1 and forwarded to the Target
BSR 220.sub.2, however non-segmented octets (i.e., PPP octets)
having a sequence number greater than V(S+x) (e.g., V(S+x+1)) are
tunnelled from the PPP (PPP.sub.1) of the Source BSR 220.sub.1 to
the PPP (PPP.sub.2) of the Target BSR 220.sub.2 to be segmented by
the RLP (RLP.sub.2) of the Target BSR 220.sub.2. The segmented
octets are then communicated by the Target BSR 220.sub.2 to the
mobile 210.
[0045] In this embodiment, because the Target F-RLP (RLP.sub.2) of
the Target BSR 220.sub.2 is servicing new octets, it will be
handling NAKs for octets with sequence numbers greater than the
sequence number V(S+x) communicated from the Source BSR 220.sub.1.
The mobile 210 and thus the R-RLP is aware of the state of the
F-RLP migration and forwards any NAKs to either the Source F-RLP
(RLP.sub.1) or the Target F-RLP (RLP.sub.2) depending on where the
missing octet is stored, which may be determined by the sequence
number of the missing octet. The Source RLP (RLP.sub.1) is now
considered to be in the Post-Serving stage of migration and
maintains a buffer of any octets having a sequence number less than
or equal to V(S+x) for which NAKs may be received. Optionally, the
F-RLP (RLP.sub.1) of the Source BSR 220.sub.1 may include a timer
to establish an amount of time for the F-RLP (RLP.sub.1) of the
Source BSR 220.sub.1 to wait for NAKs after which the F-RLP
instance of the Source BSR 220.sub.1 is deleted.
[0046] FIG. 5 depicts a high level block diagram of a method for
active session mobility for F-RLP in accordance with an embodiment
of the present invention. The method 500 begins at step 502, where
a mobile decides that it wishes to receive data from a different
source (i.e., Target BSR). The method 500 then proceeds to step
504.
[0047] At step 504, an early transfer notification (i.e., DSC
indication) is sent to all sources (i.e., BSR's) within an active
set. The method 500 then proceeds to step 506.
[0048] At step 506, a serving source (illustratively BSR 220.sub.1
in FIG. 4) decouples an RLP into a forward-link RLP (F-RLP) and a
reverse-link RLP (R-RLP) and prepares for the migration of F-RLP to
a target. More specifically, at step 506, the RLP of the source
begins to tunnel a duplicate copy of forward-link data and of its
buffer to the RLP of the target. The data, however, is not
processed at this time by the RLP of the target. The method 500
then proceeds to step 508.
[0049] At step 508, a handoff notification (e.g., a DRC) is sent to
all sources (i.e., BSR's) within an active set. The DRC defines the
target as the new serving source (illustratively BSR 220.sub.2 in
FIG. 4). The method 500 then proceeds to step 510.
[0050] At step 510, data flow to the RLP of the source halted but
the remaining data processed by the RLP of the source continues to
be tunnelled to the RLP of target. Additionally, the old source
transmits a last byte octet sequence number to the target defining
the sequence number of a last octet processed by the old source.
The source however maintains a re-transmit buffer to handle NAKs
for bytes with a sequence number less than or equal to the last
byte octet sequence number. The method then proceeds to step
512.
[0051] In an alternate embodiment of the present invention, at step
510, the contents of the re-transmit buffer of the old source, if
any, waiting for a NAK or for time-out, may be forwarded to the
target in parallel to the tunnelling of the remaining data
processed by the RLP of the old source. In this case the old source
simply forwards received NAKs to the Target, which then initiates
the retransmission. The method 500 then proceeds to step 512.
[0052] At step 512, the target receives the last byte octet
sequence number and begins processing octets having a sequence
number higher than the last byte octet sequence number. The method
500 is then exited.
[0053] FIG. 6 depicts a high level functional diagram of the BSR
network 200 of FIG. 2 after transfer of the F-RLP from the Source
BSR 220.sub.1 to the Target BSR 220.sub.2 (e.g., after the method
500 is complete). As depicted in FIG. 6, in the forward-link
direction, the HA 240 sends forward-link data to the FA (FA.sub.1)
of the Source BSR 220.sub.1. The Source FA (FA.sub.1) then sends
the forward-link data to the PPP (PPP.sub.1) of the Source BSR
220.sub.1 which tunnels the forward-link data to the PPP
(PPP.sub.2) of the Target BSR 220.sub.2. The Target PPP (PPP.sub.2)
then communicates the forward-link data to the RLP (F-RLP) of the
Target BSR 220.sub.2 which sends the forward-link data to the MAC
Scheduler (MAC/SCH.sub.2) of the Target BSR 220.sub.2 which
ultimately communicates the forward-link data to the mobile 210
over the air.
[0054] In the reverse-link direction, the mobile 210 broadcasts
reverse-link data to all of the BSRs in the active set
(illustratively BSRs 220.sub.1-220.sub.2 in FIG. 6). Each of the
Mac Schedulers (MAC/SCH.sub.1-MAC/SCH.sub.2) of the BSRs
220.sub.1-220.sub.2 communicates the received data to the RLP
(illustratively R-RLP) of the serving BSR (illustratively Source
BSR 220.sub.1) performing the Frame Selection. The Target Mac
Scheduler (MAC/SCH.sub.2) also communicates correct reverse-link
Mac Frames to the RLP (F-RLP) of the Target BSR 220.sub.2. Such an
implementation reduces the retransmission time in case any NAK is
sent by the mobile since the Target F-RLP need not wait for NAKs to
be forwarded from the Source. As such, the frame selector is being
by-passed since the Target has already received the correct
reverse-link frame. The RLP (R-RLP) of the Source BSR 220.sub.1
communicates the received data to the PPP (PPP.sub.1) of the Source
BSR 220.sub.1, which communicates the data to the FA (FA.sub.1) of
the Source BSR 220.sub.1, which communicates the data to the
intranet 230 and on up to the HA 240. As depicted in FIG. 6, it
should be noted that a communication path exists between the RLP
(R-RLP) of the Source BSR 220.sub.1 and the RLP (F-RLP) of the
Target BSR 220.sub.2 for transferring information and data such as
NAKs and missing octets, and segmented data before an
acknowledgment is received.
[0055] After the F-RLP migrates from the Source BSR 220.sub.1 to
the Target BSR 220.sub.2, the R-RLP may also be transferred from
the Source BSR 220.sub.1 to the Target BSR 220.sub.2. Prior to the
migration of the R-RLP to the Target BSR 220.sub.2, the R-RLP at
the Source BSR 220.sub.1 is operating in the Serving Stage. That
is, reverse-link octets from the mobile 210 are received at each
BSR 220.sub.1-220.sub.2 within the active set however, frame
selection continues to take place at the Source BSR 220.sub.1.
After the frame selection is completed, NAKs are forwarded to the
appropriate serving F-RLP as described above and data is sent to
the serving reverse PPP (PPP.sub.1) in the Source BSR
220.sub.1.
[0056] When a decision is made to transfer the R-RLP from the
Source BSR 220.sub.1 to the Target BSR 220.sub.2, the Source BSR
220.sub.1 informs the Target BSR 220.sub.2 of the next expected
reverse sequence number V(R) to be received by the Target BSR
220.sub.2. The Source BSR 220.sub.1 also informs all other BSRs in
the active set that Frame Selection is now taking place in the
Target BSR 220.sub.2. That is, in this embodiment of the present
invention, when the R-RLP is moved the Frame Selection is moved to
a Target BSR, substantially simultaneously.
[0057] At the instance that the R-RLP in the Source BSR 220.sub.1
becomes non-serving, at sequence number V(R), the Source BSR
220.sub.1 enters the Post-Serving Stage, where it maintains its
re-sequencing buffer and continues to receive any octets with
sequence numbers prior to V(R). Any newer octets (octets with
sequence numbers greater than V(R)) are directed toward the R-RLP
of the Target BSR 220.sub.2 which maintains its own re-sequencing
buffer. It should be noted, however, that no delivery of octets
toward the HA 240 shall occur from the Target BSR 220.sub.2 until
the Target BSR 220.sub.2 receives an indication from the R-RLP of
the Source BSR 220.sub.1 that all of its octets have either been
delivered or have timed out waiting for receipt.
[0058] The R-RLP of the Target BSR 220.sub.2 maintains awareness of
the last sequence number, V(R-1), maintained in the R-RLP of the
re-sequencing buffer of the Source BSR 220.sub.1 such that any
"old" octets (octets with a sequence number less than V(R)) may be
forwarded by the R-RLP of the Target BSR 220.sub.2 to the R-RLP of
the Source BSR 220.sub.1. Each R-RLP shall maintain its respective
re-sequencing buffer and update sequence numbers signifying the
next octet for delivery to the network. The R-RLP of the Target BSR
also maintains awareness of the F-RLP status and forwards NAKs
according to F-RLP requirements discussed previously. In addition,
when the octet having the sequence number V(R-1) is communicated to
the PPP (PPP.sub.1) of the Source BSR 220.sub.1, the Source BSR
220.sub.1 notifies the Target BSR 220.sub.2 and the PPP (PPP.sub.1)
of the Source BSR 220.sub.1 now expects the uplink data source to
be the Target BSR 220.sub.2 from the sequence number V(R) and
higher.
[0059] FIG. 7 depicts a high level block diagram of a method for
active session mobility for R-RLP in accordance with an embodiment
of the present invention. The method 700 begins at step 702, when a
decision is made to transfer the R-RLP from a Source to a Target.
The method 700 then proceeds to step 704.
[0060] At step 704, the source informs all other sources (i.e.,
BSRs) in the active set that the Frame Selection is now taking
place in the target and informs the target of the next expected
octet in the sequence V(R). The method 700 then proceeds to step
706.
[0061] At step 706, the source (i.e., Source BSR 220.sub.1)
continues to maintain its re-sequencing buffer and continues to
receive any octets with sequence numbers prior to V(R). The method
700 then proceeds to step 708.
[0062] At step 708, the target (i.e., BSR 220.sub.2) maintains its
own re-sequencing buffer and any newer octets (octets with sequence
numbers greater than V(R)) are directed toward the RLP of the
target. The method 700 then proceeds to step 710.
[0063] At step 710, when all data has been delivered by the source
or when re-sequencing in the source has timed out waiting for data,
the source informs the target that the source's R-RLP has been
completed and the R-RLP of the source is deleted. That is for
example, no delivery of octets toward the network shall occur from
the Target BSR 220.sub.2 until the Target BSR 220.sub.2 receives an
indication from the R-RLP of the Source BSR 220.sub.1 that all of
its octets have either been delivered or have timed out waiting for
receipt. The method 700 then proceeds to step 712.
[0064] At step 712, the target receives the indication that the
source has completed sending data toward the network and begins to
communicate data in its re-sequencing buffer toward the network.
The method 700 is then exited.
[0065] FIG. 8 depicts a high level functional diagram of the BSR
network 200 of FIG. 2 after the transfer of the F-RLP and R-RLP
from the Source BSR 220.sub.1 to the Target BSR 220.sub.2. As
depicted in FIG. 8, in the reverse-link direction, R-RLP data from
the mobile 210 is broadcast to all of the BSRs 220.sub.1-220.sub.3
in the active set. Each of the Mac Schedulers
(MAC/SCH.sub.1-MAC/SCH.sub.3) of the BSRs 220.sub.1-220.sub.3
communicate the received data to the RLP (illustratively RLP.sub.3)
of the serving BSR (illustratively BSR 220.sub.2) which performs
the Frame Selection. The RLP (RLP.sub.3) of the Target BSR
220.sub.2 communicates the received data to the PPP (PPP.sub.2) of
the Target BSR 220.sub.2, which tunnels the data to the PPP
(PPP.sub.1) of the Source BSR 220.sub.1. The PPP (PPP.sub.1) of the
Source BSR 220.sub.1 communicates the data to the FA (FA.sub.1) of
the Source BSR 220.sub.1, which communicates the data to the
intranet 230 and on up to the HA 240.
[0066] In the forward-link direction, the data flow is
substantially reversed. More specifically, data from the HA 240 is
communicated to the FA (FA.sub.1) of the Source BSR 220.sub.1. The
FA (FA.sub.1) communicates the data to the PPP.sub.1, which tunnels
the data to the PPP (PPP.sub.2) of the Target BSR 220.sub.2. The
PPP (PPP.sub.2) of the Target BSR 220.sub.2 communicates the data
to the RLP (RLP.sub.2) of the Target BSR 220.sub.2, which
communicates the data to the Mac Scheduler (MAC/SCH.sub.2) of the
Target BSR 220.sub.2, which communicates the data over the air to
the mobile 210.
[0067] It should be noted that although various embodiments of an
active session RLP mobility solution in accordance with the present
invention are described above as having two RLP migration states
that are migrated implementing a two-stage RLP transfer process for
the migration of the two defined states from a source to a target,
alternate embodiments of the present invention may comprise
migrating the two RLP migration states, F-RLP and R-RLP, in a
single stage implementing at least the methods for migration
described above.
[0068] As previously mentioned, in networks implementing
embodiments of an RLP mobility solution in accordance with the
present invention, a mobile may require a plurality of handoffs in
a relatively short period of time. As such, various embodiments of
RLP mobility solutions of the present invention may optionally
include a timer for deciding when to transfer the R-RLP from a
source to a target, for example, a Source BSR to a Target BSR. More
specifically, after the transfer of the F-RLP from a Source BSR to
a Target BSR, the Source BSR may initiate a timer that must expire
before the R-RLP in the Source BSR may be transferred to a Target
BSR. That is, when a mobile decides that it would like to receive
data from a Target BSR (i.e. because the mobile is receiving a
stronger signal from the Target BSR) the F-RLP in the Source BSR is
transferred to the Target BSR. However, shortly after the transfer
of the F-RLP from the Source BSR to the Target BSR, the mobile may
thereafter revert back to receiving a stronger signal from the
original Source BSR or encounter a subsequent BSR from which it is
receiving a stronger signal. As such, in embodiments of RLP
mobility solutions implementing a timer for controlling the
transfer of R-RLP, the R-RLP may be maintained in the Source BSR
for a period of time long enough for the mobile to regain a
stronger signal from the Source BSR or to attain a stronger signal
from a subsequent, second Target BSR. In the former case, the R-RLP
would remain in the Source BSR and the F-RLP may revert back to the
Source BSR. In the latter case, the F-RLP would transfer from the
Target BSR to the subsequent, second Target BSR and, if the timer
expires, the R-RLP would be transferred from the Source BSR
directly to the subsequent, second Target BSR, therefore
eliminating the need to transfer the R-RLP to the first Target BSR.
As such, the optional timer implemented in the various embodiments
of RLP mobility solutions in accordance with the present invention
may function to reduce the number of times that the R-RLP needs to
be transferred.
[0069] Similarly, a timer may be optionally implemented to control
when the F-RLP is transferred from a source to a target, for
example from a Source BSR to a Target BSR. More specifically and as
described above, a mobile may move between several data sources of
an active set in a short period of time and may even move back and
forth between various active sets. As such, a mobile may decide
that it would like to receive data from a target (i.e. because the
mobile is receiving a stronger signal from the target than from the
source). Shortly thereafter, the mobile may revert back to
receiving a stronger signal from the original source or encounter a
subsequent target from which it is receiving a stronger signal. As
such, in embodiments of RLP mobility solutions implementing a timer
for controlling the transfer of F-RLP, the F-RLP may be maintained
in the Source BSR for a period of time long enough for the mobile
to regain a stronger signal from the source or to attain a stronger
signal from a subsequent, second target. In the former case, the
F-RLP would remain in the source until the timer expires during
which time the mobile may decide to again receive data from the
source. In the latter case, the F-RLP would again remain in the
source until the expiration of the timer and only after the
expiration of the timer would the F-RLP be transferred to a target
from which the mobile is receiving its strongest signal. As such,
the optional timer implemented in the various embodiments of RLP
mobility solutions in accordance with the present invention may
function to reduce the number of times that the F-RLP needs to be
transferred.
[0070] As indicated from the disclosure above, F-RLP and R-RLP may
be moved from a source to a target and to a subsequent target
simultaneously or individually and during varying iterations. More
specifically, F-RLP and R-RLP may be transferred as described above
from a source to a first target and subsequently to a second
target, or alternatively F-RLP may be transferred to a first target
then to a second target and subsequently the R-RLP may be
transferred either to the first target and then the second target
or directly to the second target. That is, in accordance with
various embodiments of the present invention, the components of RLP
defined herein, namely F-RLP and R-RLP, may be transferred between
sources and targets simultaneously, individually or in any
combination thereof.
[0071] Although various embodiments of an active session RLP
migration solution of the present invention have been depicted with
respect to a BSR network architecture, it will be appreciated by
those skilled in the art and informed by the teachings of the
present invention that the concepts of an active session RLP
migration solution of the present invention may be applied in
substantially any network implementing a reliable protocol such as
a radio link protocol (RLP). More specifically and for example, the
concepts of an active session RLP migration solution of the present
invention may be applied in the conventional CDMA hierarchical
wireless IP network 100 of FIG. 1 to actively migrate an RLP
session among various RNCs 125 caused by, for example, the mobility
of the access terminal 110.
[0072] While the forgoing is directed to various embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof. As
such, the appropriate scope of the invention is to be determined
according to the claims, which follow.
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